fix: reject substituted ASN.1 certificate tags

[leopoldjoy]

Summary

• require exact expected ASN.1 tags at key X.509 certificate parsing boundaries
• reject constructed tag substitutions that previously could be traversed as long as their child layout matched
• add regressions for outer certificate and TBS AlgorithmIdentifier tag substitution

Security value

This reduces parser disagreement with strict X.509/DER tooling by rejecting non-certificate constructed objects instead of interpreting them as valid certificate containers.

Tests

• forge fmt --check src test
• forge test --match-test 'test_VerifyCACertWithHints_Rejects.*TagSubstitution' -vvv

Note

Latest main already fails test_DeployableContractsFitEIP170 locally with CertManager runtime bytes 24,708 > 24,576, so full-suite verification remains blocked by that pre-existing size issue.